Method of preparing 4-R-substituted 4-demethoxydaunorubicin

ABSTRACT

A method of synthesizing 4-R-substituted anthracyclines and their corresponding salts from 4-demethyldaunorubicin includes the steps of treating 4-demethyldaunorubicin with a sulfonylating agent to form 4-demethyl-4-sulfonyl-R 3 -daunorubicin. 4-Demethyl-4-R 3 -sulfonyl-daunorubicin is then subject to a reducing agent in the presence of a transition metal catalyst in a temperature range of about 30° C. to about 100° C. in a polar aprotic solvent in an inert atmosphere. Protected 4-demethoxy-4-R-daunomycin then undergoes hydrolysis in a basic solution to form the 4-R-substituted anthracyclines. The novel method lacks the step of forming a stereospecific glycoside bond between aglycone and aminoglycoside. The method also increases the yield of the final product up to 30 to 40%.

RELATED APPLICATIONS

[0001] This Application claims priority to U.S. provisional ApplicationNo. 60/472,192 filed on May 21, 2003. U.S. provisional Application No.60/472,192 is incorporated by reference as if set forth fully herein.

FIELD OF THE INVENTION

[0002] The field of the invention generally relates to chemical methodsused to produce anthracyclines. More specifically, the field of theinvention relates to methods and processes used to produce4-R-substituted 4-demethoxydaunorubicin having the formula (I) describedmore fully herein from 4-demethyldaunorubicin. In the case where R=H,the present invention relates to chemical methods and processes used toproduce idarubicin from 4-demethyldaunorubicin.

BACKGROUND OF THE INVENTION

[0003] Anthracyclines form one of the largest families of naturallyoccurring bioactive compounds. Several members of this family have shownto be clinically effective anti-neoplastic agents. These include, forexample, daunorubicin, doxorubicin, idarubicin, epirubicin, pirarubicin,zorubicin, aclarubicin, and carminomycin. For instance, these compoundshave shown to be useful in bone marrow transplants, stem celltransplantation, treatment of breast carcinoma, acute lymphocytic andnon-lymphocytic leukemia, chronic lymphocytic leukemia, non-Hodgkin'slymphoma, and other solid cancerous tumors.

[0004] Currently known methods used to prepare4-demethoxy-4-R-daunorubicin-type anthracyclines (where R=H theanthracycline is known as idarubicin) are based on coupling of theaglycone (synthesized by any of the known methods) and protected andactivated daunosamine in the presence of silver triflate (AgOSO₂CF₃),trimethylsilyltriflate ((CH₃)₃SiOSO₂CF₃), or a mercuric oxide—mercuricbromide system (HgO—HgBr₂). For example, it is currently known tosynthesize aglycone using either anthracenetetrone or isobenzofurane asthe starting substance. Unfortunately, these methods of aglyconesynthesis are complicated by the creation of optically active centers atcarbons C7 and C9.

[0005] An alternative method of synthesis of 4-demethoxydaunorubicin(idarubicin) utilizes daunorubicin aglycone which is prepared by theacidic hydrolysis of daunorubicin starting material. In this method, atthe same time daunosamine is synthesized, with chemical modification,the daunosamine can be further used for glycosylation of the modifiedaglycone. Earlier methods involved the substitution of 4-MeO aglyconesubstituent for hydrogen, NH₂, or other chemical groups involveddemethylation of daunorubicinone, sulfonation of the resulting4-demethoxydaunorubicinone and substitution of the 4-ArSO₂O radical fora 4-ArCH₂NH with further reduction of the benzyl radical leading toformation of 4-NH₂ ⁻ radical. See U.S. Pat. No. 4,085,548 entitled4-DEMETHOXY-4-AMINO-ANTHRACYCLINES, issued Jan. 15, 1991, to Caruso etal., the disclosure of which is incorporated by reference as if setforth fully herein. Further reductive deamination results in productionof 4-demethoxydaunorubicin (idarubicin). See EP Application No. 0328399,published Aug. 16, 1989, the disclosure of which is incorporated byreference as if set forth fully herein.

[0006] There also has been described a reductive cross-condensationreaction of 4-demethyl-4-Tf-daunorubicinone on the phosphoroushydride—Pd⁰ catalyzing complexes. See U.S. Pat. No. 5,587,495. In thesereactions, 4-R substituted daunorubicinones are produced wherein R=

[0007] Similarly, reductive carbonylation of 4-Tf-daunorubicinone on thesame catalysts described above results in 4-COOR substituteddaunorubicinones. See U.S. Pat. No. 5,218,130. When formate is utilizedas a ligand, substitution of 4-O-Tf radical for hydrogen takes placeresulting in formation of 4-demethoxydaunorubicinone. See U.S. Pat. No.5,103,029.

SUMMARY OF THE INVENTION

[0008] The present invention relates to processes used to prepare4-R-substituted anthracyclines and their corresponding salts of formula(I) shown below from 4-demethyldaunorubicin:

[0009] Wherein R is defined as hydrogen, a linear or branched oxy[alkyl,alkenyl or alkynyl] group comprised of one to sixteen carbon atoms, or acomplex ester group COOR₁′, wherein R₁′ is a linear or branched alkyl,alkenyl or alkyne group of up to ten carbon atoms, comprising the stepsof:

[0010] (1) providing 4-demethyldaunorubicin or a derivative of4-demethyldaunorubicin of formula (II)

[0011] wherein R₁ comprises H, acyl or acyl halide and R₂ comprises H,acyl or acyl halide, carbonate, or Schiff's base

[0012] (2) treating the 4-demethyldaunorubicin or the derivative of4-demethyldaunorubicin of formula (II) with a sulfonylating agent havinga chemical formula R₃—SO₂—X, wherein R₃ is an alkyl group, an alkylhalide group or an aryl group, X is a halide group or —O—SO₂—R₃ to form4-demethyl-4-sulfonyl-daunorubicin having formula (III)

[0013] wherein R₃ comprises an alkyl group having from 1 to 4 carbonatoms optionally substituted by one or more halogen atoms or an arylgroup optionally substituted by halogen, alkyl, aloxy or nitro, R₁comprises hydrogen, acyl, or acyl halide, and R₂ comprises hydrogen,acyl, acyl halide, carbonate, or Schiff's base;

[0014] (3) reacting the 4-demethyl-4-sulfonyl-daunorubicin of formula(III) with a reducing agent in the presence of catalytic quantities of acompound having formula (IV)

ML_(p)L′_(q)  (IV)

[0015] wherein M represent a transition metal atom; L and L′, wherein Land L′ represent the same or different anions or a neutral molecule, andp and q may vary from zero to four, to produce protected4-demethoxydaunomycin having a formula (V),

[0016] (4) hydrolyzing the protected 4-demethoxydaunomycin in a basicsolution to produce a 4-R-substituted anthracycline of formula (I).

[0017] The present invention uses a novel method of synthesis whichlacks the step of forming a stereospecific glycoside bond betweenaglycone and aminoglycoside. The inventors have found that the novelmethod of synthesis increases the yield of the final product to up to30-40% from (II). It thus is an object of the invention to provide amethod of synthesis which reduces the number of steps involved toproduce 4-R-substituted 4-demethoxydaunorubicin. It is a further objectof the invention to provide a method of synthesis which increases theyield of the process.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention is directed to methods used to prepare4-R-substituted anthracyclines and their corresponding salts of formula(I) shown below

[0019] Formula (I) illustrates a salt of a 4-R-substitutedanthracyclines. It should be understood, however, that the presentmethod contemplates the synthesis of 4-R-substituted anthracyclines offormula (I) in both the salt and non-salt forms. With respect to thesalt form shown in Formula (I), An⁻ is preferably a anion of a strongacid, for example, hydrochloric or hydrobromic acid. In Formula (I), Rmay comprise hydrogen (for example, in the case of idarubicin), a linearor branched oxy[alkyl, alkenyl, or alkynyl] group comprised of betweenone to sixteen carbon atoms. In the case of a linear or branched oxy[alkyl, alkenyl, or alkynyl] group, R preferably has less than or equalto four carbon atoms.

[0020] The linear or branched oxy[alkyl, alkenyl, or alkynyl] group maybe partially substituted for an aryl group (both unsubstituted andsubstituted) for any inert group such as, for example, an alkyl group,an alkoxy group, or a nitro group. In addition, the linear or branchedoxy group may be partially substituted for an alkoxy group, atrialkylsilyl group, ester group, or amide group.

[0021] R may also comprise a complex ester group, COOR₁′, where R₁′ is alinear or branched alkyl, alkenyl or alkyne group of up to ten carbonatoms.

[0022] The synthesis of the 4-R-substituted anthracycline of formula (I)begins by providing a starting compound, preferably4-demethyldaunorubicin or a derivative of 4-demethyldaunorubicin offormula (II)

[0023] wherein R₁ comprises H, acyl or acyl halide and R₂ comprises H,acyl or acyl halide, carbonate, or Schiff's base; (preferably COCF₃).

[0024] Next, the compound of formula (II) is treated with a sufonylatingagent having the chemical formula R₃—SO₂—X, where R₃ comprises an alkylgroup, alkyl halide group or an aryl group and X comprises a halide or—O—SO₂—R₃. The reaction is preferably conducted in pyridine in thepresence of sterically hindered tertiary amine, for example, N,N-diisoprolylethylamine, and catalytic quantities of N,N-dimethylaminopyridine. The reaction involves mostly C4-OH. Inaddition, hydroxyl groups at C6, C11 and C9 react principally in specialconditions allowing utilization of unprotected derivatives of the4-demethyldaunorubicin at these carbon positions. The above stepsproduce 4-demethyl-4-sulfonyl-daunorubicin having formula (III)

[0025] wherein R₃ comprises an alkyl group having one to four carbonatoms optionally substituted by one or more halogen atoms or an arylgroup optionally substituted by a halogen group, alkyl group, aloxygroup, or nitro group. Preferred groups for R₃ include trifluoromethyl,4-fluorophenyl, and 4-tolyl. R₁ preferably comprises hydrogen, acyl, oracyl halide. R₂ preferably comprises hydrogen, acyl, acyl halide,carbonate, or Schiff's base (i.e., a compound formed by a condensationreaction between an aromatic amine and an aldehyde or ketone).

[0026] The 4-demethyl-4-sulfonyl-daunorubicin of formula (III) us thenreacted with a reducing agent in the presence of catalytic quantities(10⁴:1 to 1:1 and preferably 20:1 to 100:1 (in a molar ratio) of acompound having formula (IV) to produce protected 4-demethoxydaunomycinhaving a formula (V).

ML_(p)L′_(q)  (IV)

[0027] wherein M represent a transition metal atom, preferably palladiumor nickel. L and L′, which are the same or different molecules,represent the same or different anions or a neutral molecule. Anions forL and L′ include anions such as HCOO⁻, CH₃COO⁻, Cl⁻. Examples of aneutral molecule include neutral solvent molecules, mono ordi-phosphine, phosphate or diamine, and preferably a chelatingdiphosphine such as 1,3-diphenylphosphinopropane,1,1′-bis(diphenylphosphino)ferrocene, and1,2-bis[N-(1-phenylethyl),N-(diphenylphosphino)amino]ethane. In formula(IV), p and q may vary from zero to four.

[0028] Preferably, the reducing agent is a formiate anion (e.g., formicacids or salts of formic acid) or unsaturated compound such as CO orsubstituted alkenyl and alkynyl groups in a reducing environment.

[0029] Preferably, the reaction is conducted at temperatures in therange from about 30° C. to about 100° C. in a polar aprotic solvent,preferably in alkylamides in an inert atmosphere. Protected4-demethoxydaunomycin having a formula (V) is shown below.

[0030] The protected 4-demethoxydaunomycin (R₁ or R₂≠H) is thenhydrolyzed to remove the protecting group in a basic solution to produce4-R-substituted anthracycline of formula (I). Preferably the basicsolution is formed in water or alcohol, preferably water or methanol.

[0031] The following examples set forth below illustrate a preferredmethod of preparing a 4-R-substituted anthracycline (idarubicin) offormula (I) from 4-demethyldaunorubicin.

EXAMPLE 1

[0032] a) First, 2 g of 3′-trifluoroacetamido-4-demethyldaunorubicin(R₁=H, R₂=trifluoroacetyl) are dissolved in 0.2 L of pyridine.

[0033] b) Next, 4 ml of diisopropylethylamine and 0.5 g of4-dimethylaminopyridine are added to the solution of step (a) of Example1.

[0034] c) Next, the solution in step (b) of Example 1 is chilled to 0°C. and 2.5 ml of freshly distilled trifluoromethanesulfonic anhydride isadded.

[0035] d) Next, the solution in step (c) of Example 1 is incubated for 1hour at room temperature.

[0036] e) After incubation, 0.15 L of concentrated hydrochloric acid,0.2 kg of ice, and 0.2 L of dichloromethane is added to the incubatedsolution.

[0037] f) Next, the organic layer is washed in 0.2 L of distilled waterand dichloromethane is removed by evaporation at partial vacuumpressure.

[0038] g) After evaporation, 1.5 g of4-trifluoromethanesulfonyl-3′-trifluoroacetamido-4-demethyldaunorubicinis produced with a purity 85% (Confirmed by HPLC).

[0039] h) The4-trifluoromethanesulfonyl-3′-trifluoroacetamido-4-demethyldaunorubicinfrom step (g) of Example 1 is used in the next synthetic step in Example2 with or without additional purification.

EXAMPLE 2

[0040] a) 1.5 g of4-trifluoromethanesulfonyl-3′-trifluoroacetamido-4-demethyldaunorubicin(R₁=H, R₂=trifluoroacetyl, R₃=trifluoromethyl), yielded from synthesisin Example 1, is dissolved in 0.1 L of dimethylformamide.

[0041] b) While stirring, 2 g of triethylamine formate and 50 mg ofpalladium acetate are added to the mixture of step (a) in Example 2 andan argon stream is passed through the mixture.

[0042] c) The mixture of step (b) of Example 2 is then heated to 50° C.and 200 mg of 1,1′-bis(diphenylphosphino)ferrocene is added.

[0043] d) The mixture of step (c) of Example 2 is heated at 50° C. for 8hours.

[0044] e) The mixture of step (d) of Example 2 is then poured into waterwith intense stirring with resulting sediment formation(4-demethoxy-3′-trifluoroacetamidodaunomycin).

[0045] f) The sediment (4-demethoxy-3′-trifluoroacetamidodaunomycin) isfiltered, and then purified by preparative chromatography.

[0046] g) The yield of this process is 0.8-0.85 g of4-demethoxy-3′-trifluoroacetamidodaunomycin of 98% purity (Confirmed byHPLC).

EXAMPLE 3

[0047] a) 0.85 g of 4-demethoxy-3′-trifluoroacetamidodaunomycin areadded to the stirred water solution of 0.1 N NaOH (0.06 L) and incubatedat 30° C. for 30 minutes. The color of the solution turns deepblue-violet.

[0048] b) The reactive mixture is then poured with intense stirring into0.5 L of 10-12% chloroform-in-butanol solution heated to 40° C.

[0049] c) Next, while intensely stirring, hydrochloric acid (1:3) isadded to the mixture to titrate to a pH of 8.8-9.0.

[0050] d) The resulting organic layer is then washed in distilled water.

[0051] e) 0.1 L of distilled water is then added to washed organic layerin step (d) of Example 3, and 0.8 N hydrochloric acid is added (0.1 L)to titrate to a pH of 3.5.

[0052] f) The solution in step (e) in Example 3 is intensely stirred,and the water layer containing 4-demethoxydaunomycin hydrochloride(idarubicin) is separated.

[0053] g) The solution of idarubicin hydrochloride is evaporated to 50%of its original volume and was subjected to chromatographicpurification.

[0054] h) The eluate was subjected to evaporation and crystallizationusing hydrophilic solvents, preferably low-molecular-weight aliphaticalcohols.

[0055] i) The yield of this process is 0.6 g of 4-demethoxydaunomycinhydrochloride (idarubicin hydrochloride) of 99% purity (Confirmed byHPLC).

[0056] While embodiments of the present invention have been shown anddescribed, various modifications may be made without departing from thescope of the present invention. The invention, therefore, should not belimited, except to the following claims, and their equivalents.

We claim:
 1. A process for preparing 4-R-substituted anthracyclines offormula (I)

wherein R is defined as hydrogen, a linear or branched oxy[alkyl,alkenyl or alkynyl] group comprised of one to sixteen carbon atoms, or acomplex ester group COOR₁′, wherein R₁′ is a linear or branched alkyl,alkenyl or alkyne group of up to ten carbon atoms, comprising the stepsof: (1) providing 4-demethyldaunorubicin or a derivative of4-demethyldaunorubicin of formula (II)

wherein R₁ comprises H, acyl or acyl halide and R₂ comprises H, acyl oracyl halide, carbonate, or Schiff's base; (2) treating the4-demethyldaunorubicin or the derivative of 4-demethyldaunorubicin offormula (II) with a sulfonylating agent having a chemical formulaR₃—SO₂—X, wherein R₃ comprises an acyl group, acyl halide group or arylgroup, X comprises a halide or —O—SO₂—R₃ to form4-demethyl-4-sulfonyl-daunorubicin having formula (III)

wherein R₃ comprises an alkyl group, alkyl halide group or an arylgroup, R₁ comprises hydrogen, acyl, or acyl halide, and R₂ compriseshydrogen, acyl, acyl halide, carbonate, or Schiff's base; (3) reactingthe 4-demethyl-4-sulfonyl-daunorubicin of formula (III) with a reducingagent in the presence of catalytic quantities of a compound havingformula (IV) ML_(p)L′_(q)  (IV) wherein M represent a transition metalatom; L and L′, wherein L and L′ represent the same or different anionsor a neutral molecule, and p and q may vary from zero to four, toproduce protected 4-demethoxydaunomycin having a formula (V),

(4) hydrolyzing the protected 4-demethoxydaunomycin in a basic solutionto produce 4-R-substituted anthracyclines of formula (I).
 2. The processof claim 1, wherein transition metal M comprises palladium.
 3. Theprocess of claim 1, wherein transition metal M comprises nickel.
 4. Theprocess of claim 1, wherein L comprises an anion selected from the groupconsisting of HCOO⁻, CH3COO⁻, Cl⁻, a neutral solvent molecule,monophosphine, diphosphine, phosphate, and diamine.
 5. The process ofclaim 4, wherein L comprises a chelating diphosphine selected from thegroup consisting of 1,3-diphenylphosphinopropane,1,1′-bis(diphenylphosphino)ferrocene, and1,2-bis[N-(1-phenylethyl),N-(diphenylphosphino)amino]ethane.
 6. Theprocess of claim 1, wherein L′ comprises an anion selected from thegroup consisting of HCOO⁻, CH3COO⁻, Cl⁻, a neutral solvent molecule,monophosphine, diphosphine, phosphate, and diamine.
 7. The process ofclaim 6, wherein L′ comprises a chelating diphosphine selected from thegroup consisting of 1,3-diphenylphosphinopropane,1,1′-bis(diphenylphosphino)ferrocene, and1,2-bis[N-(1-phenylethyl),N-(diphenylphosphino)amino]ethane.
 8. Theprocess of claim 1, wherein the reducing agent comprises formic acid orsalts of formic acid.
 9. The process of claim 1, wherein R in formula(I) comprises a linear or branched oxy[alkyl, alkenyl or alkynyl] groupcomprised of one to sixteen carbon atoms.
 10. The process of claim 9,wherein R in formula (I) comprises a linear or branched oxy[alkyl,alkenyl or alkynyl] group comprised of one to sixteen carbon atomspartially substituted by a group consisting of an aryl group, an alkoxygroup, a trialkysilyl group, an ester group, and an amide group.
 11. Theprocess of claim 1, wherein R comprises a complex ester group COOR₁′,wherein R₁′ is a linear or branched alkyl, alkenyl or alkyne group of upto ten carbon atoms.
 12. A process for preparing idarubicin of formula(I)

wherein R is H and An⁻ comprises an anion of an acid, comprising thesteps of: (1) providing 4-demethyldaunorubicin or a derivative of4-demethyldaunorubicin of formula (II)

wherein R₁ comprises H and R₂ comprises trifluoroacetyl, (2) treatingthe 4-demethyldaunorubicin or the derivative of 4-demethyldaunorubicinof formula (II) with a sulfonylating agent comprisingtrifluoromethanesulfonic anhydride to form4-trifluoromethanesulfonyl-3′-trifluoroacetamido-4-demethyldaunorubicin,(3) reacting the4-trifluoromethanesulfonyl-3′-trifluoroacetamido-4-demethyldaunorubicinwith a reducing agent in the presence of catalytic quantities ofpalladium acetate to produce4-demethoxy-3′-trifluoroacetamidodaunomycin, and (4) hydrolyzing the4-demethoxy-3′-trifluoroacetamidodaunomycin in a basic solution toproduce idarubicin of formula (I).
 13. The process of claim 12, whereinidarubicin of formula (I) comprises idarubicin hydrochloride.